GB2072874A

GB2072874A - Three-dimensional projection

Info

Publication number: GB2072874A
Application number: GB8107762A
Authority: GB
Original assignee: Hedley D G
Current assignee: Hedley D G
Priority date: 1980-03-27
Filing date: 1981-03-12
Publication date: 1981-10-07
Also published as: GB2072874B

Abstract

Right and left images are projected by projectors (16, 18) onto a screen (10) whose surface is composed of two sets of mutually- angled vertical strips (12, 14). The strips are angled such that one set (12) receives light only from the right image projector (16), and the other set (14) only from the left image projector (18). An observer in front of the screen perceives a three-dimensional image. <IMAGE>

Description

SPECIFICATION Three-dimensional projection

Description This invention relates to three-dimensional (3-D) projection of images, either still or moving.

There are various well-known methods of producing 3-D image. In one approach, still or cine pictures are taken by a double camera and the resulting left and right images are distinguished by polarisation or differential colouring. However, viewing requires the use of polarised or coloured spectacles, which is inconvenient and hinders customer acceptance.

Another approach is by laser holography, but this has limitations as regards image size and colour, and also involves relatively complex and expensive apparatus.

An object of the invention is to provide an improved 3-D projection system.

One aspect of the invention accordingly provides a 3-D viewing system comprising two projectors and a screen, the projectors being aligned at angles to the screen, and the screen being corrugated to provide interleaved sets of strips, the strips of one set facing one projector and being substantially aligned with the other projector, and vice versa.

Preferably, the projectors are each at 450 to the screen and at 90" to each other. The strips may suitably be at 450 to the general plane of the screen and at 900 to each other.

In another aspect, the invention provides a corrugated screen as defined above.

Embodiments of the present invention will now be described with reference to the accompanying diagrammatic drawings, in which: Fig. 1 is a schematic plan view of one form of the invention; Fig. 2 is a schematic plan view of a modified form of screen; Fig. 3 illustrates distortion which may occur in the projected images; and Fig. 4 is a diagrammatic plan view of the invention applied to a television type display.

Fig. 1 shows one form of the invention in schematic outline. A screen 10 has its viewing surface formed of vertical strips 12 and 14 which are mutually perpendicular and each at 450 to the general plane of the screen. Two projectors 1 6, 1 8 are arranged with their projection axes at 450 to the screen 10. The projectors 16, 1 8 may be slide or cine projectors, and project left and right images taken on known 3-D cameras.

The arrangement of the projectors 16, 1 8 relative to the screen is such that the left image falls on one set of strips 1 2 and the right image on the other set of strips 1 4 only. Thus a viewer positioned in front of the screen as indicated experiences a 3-D image.

The corrugations in the screen 10 are greatly exaggerated in Fig. 1 for clarity. In practice, the width of each strip would be from 0.1 mm or less to a maximum of 6mm.

Some modifications to the basic system of Fig.

1 are as follows.

The angle of the faces can be gradually altered across the screen as shown in Fig. 2 so that every face is at right angles to the light falling on it.

For each projector, the light intensity at one side of the screen will be greater than at the other side owing to the greater distance. Any visible reduction in picture quality resulting from this can be accommodated by increasing the reflectance of the respective strips with increasing projection distance.

The same variation in projection distance could cause problems in focusing at the sides of the screen. This can be met by using a small aperture projecting lens and a high intensity light source, to give a depth of focus sufficiently large to include the entire screen.

The screen can be manufactured by machining or moulding. The viewing surface is suitably coated with a known omni-directional reflective substance, or simply white paint.

Owing to the angle of the projection, there will be a sideways keystone distortion which may be visible to the viewer depending on the relative distances of the viewer and the projectors to the screen, as indicated in Fig. 3 where 20 indicates the image from the left projector and 22 the image of the right projectors. This can be obviated by using at each projector an anamorphic projection lens with an opposite distortion, as indicated at 24 in Fig. 1.

When setting up the projection system, the projectors can be operated to project the same picture on a plain screen to achieve exact registration, the screen then being replaced by the present screen.

The present invention could equally be applied to rear projection, as will be readily understood by analogy with the above description of front projection.

In a similar manner, it could be applied to a television tube display as illustrated in Fig. 4. An evacuated tube 40 has electron guns 42, 44 and a screen 46. The rear surface of the screen 46 is formed into angled vertical strips 48, and is coated with the usual phosphor material. The electron guns 42, 44 have conventional deflection coils, but the driving of these coils may be non-linear to compensate for keystone distortion. Again, the size of the strips 48 is greatly exaggerated in Fig.

4. The electron guns 42, 44 could be tricolour guns; in this case, it would be necessary to provide the screen 46 with red, blue and green phosphor triads and include a shadowmask (not shown), as is well known in the art.

CLAIMS 1. A 3-D viewing system comprising two projectors and a screen, the projectors being -aligned at angles to the screen, and the screen being corrugated to provide interleaved sets of strips, the strips of one set facing one projector and being substantially aligned with the other projector, and vice versa.

2. The system of claim 1, in which the

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Three-dimensional projection Description This invention relates to three-dimensional (3-D) projection of images, either still or moving. There are various well-known methods of producing 3-D image. In one approach, still or cine pictures are taken by a double camera and the resulting left and right images are distinguished by polarisation or differential colouring. However, viewing requires the use of polarised or coloured spectacles, which is inconvenient and hinders customer acceptance. Another approach is by laser holography, but this has limitations as regards image size and colour, and also involves relatively complex and expensive apparatus. An object of the invention is to provide an improved 3-D projection system. One aspect of the invention accordingly provides a 3-D viewing system comprising two projectors and a screen, the projectors being aligned at angles to the screen, and the screen being corrugated to provide interleaved sets of strips, the strips of one set facing one projector and being substantially aligned with the other projector, and vice versa. Preferably, the projectors are each at 450 to the screen and at 90" to each other. The strips may suitably be at 450 to the general plane of the screen and at 900 to each other. In another aspect, the invention provides a corrugated screen as defined above. Embodiments of the present invention will now be described with reference to the accompanying diagrammatic drawings, in which: Fig. 1 is a schematic plan view of one form of the invention; Fig. 2 is a schematic plan view of a modified form of screen; Fig. 3 illustrates distortion which may occur in the projected images; and Fig. 4 is a diagrammatic plan view of the invention applied to a television type display. Fig. 1 shows one form of the invention in schematic outline. A screen 10 has its viewing surface formed of vertical strips 12 and 14 which are mutually perpendicular and each at 450 to the general plane of the screen. Two projectors 1 6, 1 8 are arranged with their projection axes at 450 to the screen 10. The projectors 16, 1 8 may be slide or cine projectors, and project left and right images taken on known 3-D cameras. The arrangement of the projectors 16, 1 8 relative to the screen is such that the left image falls on one set of strips 1 2 and the right image on the other set of strips 1 4 only. Thus a viewer positioned in front of the screen as indicated experiences a 3-D image. The corrugations in the screen 10 are greatly exaggerated in Fig. 1 for clarity. In practice, the width of each strip would be from 0.1 mm or less to a maximum of 6mm. Some modifications to the basic system of Fig.

1 are as follows.

2. The system of claim 1, in which the

projectors are each at 450 to the screen and at 900 to each other.

3. The system of claim 2, in which the strips are at 450 to the general plane of the screen and at 900 to each other.

4. The system of claim 1 or claim 2, in which the strips are at an angle to the general plane of the screen which decreases with distance from the centre of the screen.

5. The system of any preceding claim, in which each projector is provided with an anamorphic lens to counteract keystone distortion.

6. The system of any preceding claim, in which the projectors are optical projectors which project from photographic transparencies for viewing from the front of the screen.

7. The system of any of claims 1 to 5, in which the projectors are electron guns and the strips are formed in the rear surface of a viewing screen and are coated with phosphors.

8. A screen for use in the system of claim 1, comprising a corrugated surface providing interleaved plane strips, alternate strips being set at an angle to each other.

9. The screen of claim 8, in which the width of the strips is about 0.1 mm.